What adjustments can be made to a patient's Tandem T slim (insulin pump) settings, with current basal rates of 0.9 and 1.00 units per hour, correction factors (CF) of 1:28 and 1:32, and carb ratios of 1:10 and 1:12, to prevent occasional nocturnal hypoglycemia while in sleep mode?

Adjusting Tandem T:slim Settings to Prevent Nocturnal Hypoglycemia in Sleep Mode

Immediate Basal Rate Reduction Required

Your patient's nocturnal hypoglycemia while in sleep mode indicates the overnight basal rates (0.9 and 1.00 units/hour) are too high and must be reduced immediately. 1

Calculate Current Overnight Basal Delivery

• If running 0.9-1.00 units/hour for approximately 8 hours overnight, this delivers 7.2-8.0 units of basal insulin during sleep 2, 3
• Sleep mode on Tandem pumps typically reduces insulin delivery by 30%, but this may still be insufficient if the baseline basal rates are set too high 1

Recommended Basal Rate Adjustment Protocol

Reduce overnight basal rates by 10-20% immediately (to approximately 0.72-0.90 units/hour for the 0.9 rate and 0.80-0.90 units/hour for the 1.00 rate) 1, 4

• Make adjustments in 0.05-0.10 unit/hour increments every 3 days based on overnight glucose patterns 1, 2
• Target fasting glucose should be 80-130 mg/dL (4.4-7.2 mmol/L) 1
• If hypoglycemia occurs without clear cause, reduce the dose by an additional 10-20% immediately 1, 4

Verify Basal Rate Appropriateness Through Testing

Conduct a formal basal rate assessment to confirm optimal overnight settings 1

• Blood glucose should vary by no more than 30 mg/dL (1.7 mmol/L) throughout a 4-hour fasting period if basal rates are correct 1
• Test overnight by checking glucose at midnight, 3 AM, 6 AM, and upon waking 1
• Any significant deviation or hypoglycemia requires consultation and basal rate reduction before continuing current settings 1

Evaluate Total Daily Insulin Dose Context

Assess whether total basal insulin represents an appropriate percentage of total daily dose (TDD) 2, 3, 5

• Basal insulin should comprise approximately 40-50% of TDD in pump therapy, though recent evidence suggests 30-48% may be more appropriate to avoid overinsulinization 2, 3
• Calculate total basal delivery: If running 0.9-1.00 units/hour for 24 hours, this equals 21.6-24.0 units/day of basal insulin 2
• If this represents >50% of TDD, the patient is likely running supraphysiological basal rates and attempting to compensate for inadequate bolus coverage with excessive basal insulin 2, 3

Address Correction Factor and Carb Ratio Settings

Your correction factors (1:28 and 1:32) and carb ratios (1:10 and 1:12) appear reasonable but should be verified against TDD 3

• Correction factor formula: 1800-2000/TDD 3
• Carb ratio formula: 450-500/TDD for rapid-acting insulin 3
• If these ratios are significantly different from calculated values, the patient may be under-bolusing for meals and compensating with excessive basal rates 2, 3

Critical Safety Considerations for Sleep Mode

Sleep mode reduces insulin delivery but does not eliminate the need for appropriate baseline basal rates 1

• Automated insulin suspension features in hybrid closed-loop systems reduce nocturnal hypoglycemia, but only when baseline settings are appropriate 1
• The system cannot fully compensate for basal rates that are fundamentally too high 1
• Continuous glucose monitoring data should demonstrate stable overnight glucose readings without significant drops 1

Common Pitfalls to Avoid

Do not attempt to correct nocturnal hypoglycemia by adjusting only the correction factor or carb ratios - this is a basal rate problem requiring basal rate adjustment 1, 2

Avoid running supraphysiological basal rates in an attempt to lower average glucose - this leads to increased hypoglycemia risk and glucose variability 2

Do not disconnect from the pump overnight to avoid lows - this causes relative insulin deficiency within 1 hour and can lead to ketosis 2

Ensure the pump's internal clock is set correctly - incorrect time settings can cause inappropriate basal rate delivery if different rates are programmed for different times of day 6

Monitoring Requirements During Adjustment

Check glucose at midnight, 3 AM, and upon waking for at least 3 consecutive nights after each basal rate change 1

• Document all episodes of hypoglycemia (glucose <70 mg/dL) 1
• Reassess basal rates every 3 days during active titration 1, 2
• Consider using continuous glucose monitoring downloads to visualize overnight patterns 1

When to Consider Additional Interventions

If nocturnal hypoglycemia persists despite appropriate basal rate reductions, evaluate for:

• Dawn phenomenon requiring higher basal rates in early morning hours (4-8 AM) versus lower rates during deep sleep (midnight-4 AM) 2
• Exercise effects from late afternoon/evening activity increasing insulin sensitivity overnight 1
• Alcohol consumption, which can cause delayed hypoglycemia 1
• Inadequate bedtime snack if going to bed with glucose <120 mg/dL 1